A kind of hydraulic control device of a lockup clutch has a lockup clutch, a first oil passage, a second oil passage, and a third oil passage. The lockup clutch is included in a fluid-type power transmitting device such as a torque converter and a fluid coupling and is engaged and released based on oil pressure. The first oil passage is communicated with an engagement-side oil chamber of the lockup clutch to supply an engagement oil pressure to the engagement-side oil chamber at the engagement of the lockup clutch. The second oil passage is communicated with a release-side oil chamber of the lockup clutch to supply a release oil pressure to the release-side oil chamber at the release of the lockup clutch. The third oil passage is communicated with the engagement-side oil chamber of the lockup clutch to discharge operating oil in the engagement-side oil chamber at the engagement of the lockup clutch. A device described in Patent Document 1 is an example of such a hydraulic control device and operating oil is discharged from the third oil passage and returned through an oil cooler to an oil pan at both the engagement and the release of the lockup clutch.
Patent Document 1: Japanese Patent Application Laid-Open Publication No. 63-190972